1. Field of the Invention
This invention relates to switching type power supplies and more particularly to a circuit adapted for use therein which increases the efficiency of the supply when it operates at or below some predetermined low power level.
2. Description of the Prior Art
Switching type power supplies are used in the telephone art to provide a variety of voltages to a load. For example, a switching type power supply in the form of a d-c to d-c converter may be used to provide ringing voltage and current (power) to the subscribers of a central office powered multichannel subscriber carrier system. The converter may have to provide a peak load power which is substantially higher than the relatively low load power it normally provides. Ordinarily such converters are designed to have a relatively high efficiency and good stability when they provide such peak power. When such a converter provides the normal and relatively low load power, the efficiency and stability both decrease by substantial amounts.
In the past it has been the practice to design the converter for the desired high efficiency at peak power levels and "live with" the substantially lower and therefore poorer efficiency at the lower power levels. It has, however, been recognized that the circuit of the present invention will increase the efficiency of the converter at such low power levels to be close to the efficiency at the higher or peak power levels.